BENEFITING FROM ENERGY CONSERVATION IN RETAIL ESTABLISHMENTS
Global Energy Challenges Eradicating Energy PovertyMobilizing Capital for Energy InfrastructureAchieving Energy SecurityAchieving Energy Sustainability and Climate Stability
Energizing DevelopmentThe provision of energy services is a vital precursor to economic developmentUNDP, Human Development Index
Proven Gas ReservesUltimate remaining resources (including proven reserves) are an estimated 453 - 527 tcm
Atmospheric Carbon Dioxide (CO2) ConcentrationsSource: C.D. Keeling and T.P. Whorf, Atmospheric CO2 Concentrations (ppmv) derived from in situ air samples collected at Mauna Loa Observatory, Hawaii, Scripps Institute of Oceanography, August 1998. A. Neftel et al, Historical CO2 Record from the Siple Station Ice Core, Physics Institute, University of Bern, Switzerland, September 1994. See http://cdiac.esd.ornl.gov/trends/co2/contents.htm
The Technology ApproachHydrogen Fuel Cell VehiclesZero Net Emission BuildingsNuclear Power Generation IVRenewable Energy TechnologiesVision 21: Zero-Emission Power PlantBio-Fuels and PowerCarbon (CO2) SequestrationDeep cuts in emissions requireadvanced technologiesSOONNo single technologycan do it all
ENERGY AUDIT IN RETAIL OUTLETSMAJOR ENERGY CONSUMPTION AREAS IN RETAIL OUTLETS ARE :
REFRIGERATION AND AIR CONDITIONING LIGHTING SYSTEMS OTHERS ( ESCALATORS, LIFTS, COMPUTERS, ETC.)
REFRIGERATION & AIR CONDITIONING (AC) SYSTEMSREFRIGERATION AND AC SYSTEMS ARE OF 2 TYPES
VAPOUR COMPRESSION REFRIGERATION SYSTEMS (VCS) : Use Compressors
VAPOUR ABSORPTION REFRIGERATION SYSTEM (VAS) : Used where process waste heat or cheap fuels are available
WHAT IS A TON OF REFRIGERATION? The cooling effect produced is quantified as tons of refrigeration.Coefficient of Performance (COP) - If both refrigeration effect and the work done by the compressor (or the input power) are taken in the same units (TR or kcal/hr or kW or Btu/hr), the ratio isCOP = Refrigeration Effect / Work done
Specific Power Consumption = Power Consumption (kW) / Refrigeration effect (TR)
Lower Specific Power Consumption implies better efficiency.
VAPOUR COMPRESSION REFRIGERATION SYSTEM : Components and Principle
VAPOUR COMPRESSION REFRIGERATION SYSTEM
REFRIGERANTS : OZONE DEPLETION AND GLOBAL WARMINGRefrigerants are substances with low boiling points and large latent heats, at pressures above atmospheric pressure. They usually fall under one of the following groups:CFCs ChlorofluorocarbonsHCFCs hydro chlorofluorocarbonsHFCs Hydro fluorocarbonsHCs HydrocarbonsNH3 - AmmoniaCFCs deplete ozone layer and are phased out under Montreal ProtocolHCFCs deplete carbon but to a later extent and would be totally phased out by 2015CFCs and HCFCs are replaced by HFCs which were developed as recent as 1990
Vapour Compression CycleFluorinated halocarbons are nontoxic, nonflammable, noncombustible and non-corrosive but when released into atmosphere they damage the ozone layer.
Ammonia, Refrigerant R-717, now limited to the industrial applications because of its high toxicity.
Vapour Absorption CycleAmmonia is a refrigerant used with water as the absorbent ( solvent). Use of ammonia is declining with the introduction of refrigerants that have low toxicity and operate at lower system pressures.
Water is most common refrigerant, and is used in combination with lithium bromide as absorbent.
Brines and Secondary Coolants :These liquids are cooled or heated by the primary refrigerant and transfer heat energy without change of state. COMMONLY USED REFRIGERANTS
The refrigerant type can affect the efficiency of the system by about 10%.
Too much or too little charge of refrigerant can reduce efficiency.
Insufficient refrigerant reduces the wetted area of the evaporator, increases the superheat, reduces the suction pressure, increases the temperature and reduces the efficiency.
Refrigerant, contaminated with air or other gases, will affect the efficiency of the system.EFFECT OF REFRIGERANTS ON EFFICIENCY OF THE SYSTEM
PERFORMANCE OF VAPOUR COMPRESSION REFRIGERATION SYSTEMEfficiency of the Vapour Compression Refrigeration System is dependent on the performance of the following :
COMPRESSOR CONDENSER, COOING TOWER EVAPORATOR EXPANSION VALVE
COMPRESSORSGENERALLY THERE ARE 4 TYPES OF COMPRESSORS USED- CENTRIFUGAL COMPRESSORS- RECIPROCATING COMPRESSORS- SCREW COMPRESSORS- SCROLL COMPRESSORS
These are further classified as -Hermetic Compressors : compressor, motor, shaft and drive are sealed in a welded casing to contain the refrigerant and lubricating oil -Semi Hermetic Compressor : similar to hermetic but motor and compressor are in fabricated enclosure with bolted sections-Open Compressors: external drive shaft that extends through a seal in compressor housing
EVAPORATORSEVAPORATOR IS A HEAT EXCHANGER WHERE HEAT IS REMOVED FROM THE SYSTEM (AIR , WATER OR OTHER INTERMEDIATE FLUID) BY THE BOILING OF REFRIGERANT IN THE EVAPORATORHEAT TRANSFER RATES IN EVAPORATOR DEPENDS ON SURFACE AREA, FLUIDS INVOLVED, TURBULENCE IN FLUID STREAMS AND OPERATING TEMPERATURE AND PRESSURE1) The Evaporator may be refrigerant cooled coils in an air stream (Air Handling Unit- AHU) for Air Conditioning
The Evaporator may be PLATE HEAT EXCHANGERThe Evaporator may be SHELL & TUBE HEAT EXCHANGERS with refrigerant in shell or tube sides EVAPORATORS
The Evaporator may be refrigerants coils (DIRECT EXPANSION (DX) COILS) submerged in water or brine tanksDirect expansion (DX) coils consist of a series of tubes through which refrigerant flows. The tubes are arranged into a number of parallel circuits fed from a single expansion valve. The hot refrigerant vapour is collected in the outlet (suction) gas header. The tubes are finned to increase the heat transfer rate from the medium to be cooled, generally air, to the boiling refrigerant.
Effect of Variation in Evaporator Temperature on Compressor Power Consumption 10C raise in evaporator temperature can help to save almost 3 % on power consumption.
Evaporator Temperature (0C)
Refrigeration Capacity (tons)
Specific Power Consumption
Increase in kW/ton (%)
A water cooled condenser is generally in loop with a cooling towerAuxiliary pumps and piping for recirculation of cooling water are required.Water treatment is required in water recirculation systems.Space requirements.Maintenance problems.Freeze protection for winter operation.WATER-COOLED CONDENSERS
Low installation costs, Low maintenance requirements.,Higher power requirements per kW cooling than evaporative or water-cooled condensers.Operating difficulties caused by increased condensing capacity and lower loads when operating at low ambient temperatures.Multiple units are required in large systems.AIR-COOLED CONDENSERS
EVAPORATIVE CONDENSERSIndoor locations are possible.Water treatment is required.Space requirements are less than for air-cooled condensers, or shell and tube condensers when a cooling tower is used.For a given capacity, less circulating water is required than for a water cooled condenser with a cooling towerSystem pumps are smaller
Effect of Variation in Condenser Temperature on Compressor Power Consumption
Condensing Temperature (0C)
Refrigeration Capacity (tons)
Specific Power Consumption
Increase in kW/TR (%)
Effect of Poor Maintenance on Compressor Power Consumption
Evap. Temp (0C)
Cond. Temp (0C)
Refrigeration Capacity (tons)
Specific Power Consumption (kW/ton)
Increase in kW/Ton (%)
Dirty condenser and evaporator
COOLING TOWERS1 deg C cooling water temperature increase may increase A/C compressor kW by 2.7%.
Performance ParametersRange is the difference between the cooling water inlet and outlet temperatureFormula:CT Range (C) = [CW inlet temp (C) CW outlet temp (C)]Approach is the difference between the cooling tower outlet cold water temperature and ambient wet bulb temperature
Formula:CT Approach (C) = [CW outlet temp (C) Wet bulb temp (C)]
Performance ParametersCooling tower effectiveness (%) is the ratio of range to the ideal range -the difference between cooling water inlet temperature and ambient wet bulb temperatureFormula:CT Effectiveness (%) = 100 x (CW temp CW out temp) / (CW in temp WB temp)Cooling capacity is the heat rejected in kCal/hr or TR -given as product of mass flow rate of water, specific heat and temperature difference
Performance Parameterse) Evaporation loss is the water quantity evaporated for cooling duty theoretically, for every 10,000,000 kCal heat rejected, evaporation quantity works out to 1.8 m3An empirical relation: Evaporation Loss (m3/hr) = 0.00085 x 1.8 x circulation rate (m3/hr) x (T1-T2)T1-T2 = Temp. difference between inlet and outl